Integrated Circuit Stacked Package Precursors and Stacked Packaged Devices and Systems Therefrom

ABSTRACT

A package-on-package (POP) package precursor and packaged devices and systems therefrom includes an electronic substrate including electrically conductive layers and a top surface. A first portion of the top surface has an IC die attached thereon. A second portion of the top surface has a plurality of first attach pads on opposing sides of the IC die for electrically coupling to a first electronic device on top of the IC die. At least a third portion of the top surface is positioned laterally with respect to the first and second portion. The third portion includes a plurality of second attach pads for electrically coupling to at least a second electronic device. At least one of the electrically conductive layers includes a coupling trace that couples at least one of the plurality of second attach pads to the IC die and/or one or more of the plurality of first attach pads.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/388,976filed Feb. 19, 2009 and claims priority to the following United Statesprovisional patent applications, (i) 61/029,812 filed Feb. 19, 2008,entitled “Stacked Package with Multiple Active and Passive Elements”,(ii) 61/029,814, filed Feb. 19, 2008, entitled “Stacked Package withMemory and Passive Elements”, and (iii) 61/141,735 entitled “IntegratedCircuit Package” filed Dec. 31, 2008, all incorporated herein in theirentireties into the present application.

FIELD OF THE INVENTION

Embodiments of the present invention are directed to integrated circuit(IC) comprising lateral stacked package precursors and IC comprisinglateral stacked packages therefrom, and more particularly to ICcomprising lateral stacked package precursors and IC comprising lateralstacked packages therefrom having both RF active and RF passive circuitelements.

BACKGROUND

As the demand for faster, smaller electronic products with increasedfunctionality is increased, stacked packaging schemes, such aspackage-on-package (POP) packaging, have become increasingly popular.The stacking of different semiconductor packages using stacked packagestypically reduces the required footprint size for a semiconductorpackage in an electronic product. Furthermore, stacked packages canprovide a modular solution for constructing electronic devices bypermitting different combinations of stacked semiconductor packagesusing only a few semiconductor package footprints.

Many advanced electronic packages and devices typically include analogand digital circuits in the same electronic device or system. In theseso-called “mixed-signal” devices, signals are typically susceptible todegradation as the signals traverse the various components of theelectronic device. Furthermore, the analog signals are generallysusceptible to electromagnetic interference (EMI) and the presence ofdigital signals in the vicinity of the analog components. Thissusceptibility generally allows the EMI from the digital circuits tocouple directly into the analog sections of the mixed-signal device,generally resulting in noise being introduced into the analog signals.

For example, even though typical CMOS digital devices in a high speeddigital circuit generally have a low quiescent current, simultaneousswitching noise (SSN, also known as ground bounce) caused by the CMOScircuit switching current, can be a significant source of EMI to theanalog section of mixed signal device leading to increased noise.Additionally, some analog signals can be susceptible to EMI caused byhigh level signals from other analog circuits, particularly those whichswing nearly a full supply voltage range, also resulting in increasednoise.

SUMMARY OF THE INVENTION

This Summary is provided to comply with 37 C.F.R. §1.73, providing asummary of the invention briefly indicating the nature and substance ofthe invention. It is submitted with the understanding that it will notbe used to interpret or limit the scope or meaning of the claims.

A first embodiment of the present invention comprises apackage-on-package (POP) package precursor. As used herein, a “POPprecursor” refers to a partially completed IC comprising device thatgenerally includes an electronic board substrate (e.g. PCB) having atleast one IC die attached thereon, first attach pads configured forlater mounting a first IC on top of the assembled IC to form a firstPOP, and a lateral portion of the board having second attach pads formounting passives and/or other ICs and optionally stacking additionaldevices thereon to form a second POP.

The electronic board substrate includes a plurality of electricallyconductive layers (e.g. metal traces) that provides electrical couplingbetween the IC and the attached pads. The first IC is coupled to thefirst attach pads, and the passives and/or other ICs device(s) arecoupled to the second attach pads. In a typical application, a customerobtains a POP package precursor according to an embodiment of theinvention, and adds or has a sub-contractor add circuitry to customizethe POP precursor to provide a finished system in a package (SIP), suchas by adding a memory module on the IC die, and RF circuitry on thesecond pads on the lateral portion.

In other embodiments of the present invention, a package-on-package(POP) comprising IC comprises an electronic substrate comprising aplurality of electrically conductive layers separated by a plurality ofdielectric layers. The electronic substrate provides a top surface. Afirst portion of the top surface has an IC die attached thereonelectrically coupled thereto. A second portion of the top surface has aplurality of first attach pads positioned on opposing sides of the ICdie having exposed electrically conductive surfaces. At least a firstelectronic device is coupled to the plurality of first attach pads andpositioned on top of the IC die. A least a third portion of the topsurface is positioned laterally with respect to the first and secondportion of the top surface, wherein the third portion includes aplurality of second attach pads having exposed electrically conductivesurfaces. At least a second electronic device electrically is coupled tothe second attach pads. At least one of the plurality of electricallyconductive layers comprises a coupling trace that electrically couplesat least one of the plurality of second attach pads to at least one ofthe IC die and at least one of the plurality of first attach pads. Inone embodiment the POP IC comprises a memory module (SRAM, DRAM or flashmemory), an ASIC module (baseband processor, applications processordigital radio, BT/FM/GPS) and an RF module including an RF transceiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a cross sectional view of an exemplary package-on-package(POP) package precursor having a flip chip IC die, according to anembodiment of the invention.

FIG. 1B shows a cross sectional view of an exemplary POP packageprecursor having a face up IC die that includes through wafer vias,according to an embodiment of the invention.

FIG. 2A shows a cross-section of an exemplary IC device arrangedaccording to an embodiment of the present invention.

FIG. 2B shows a top-down view of a portion of an exemplary IC devicearranged according to an embodiment of the present invention.

FIG. 3A shows a cross-section of an exemplary IC device arrangedaccording to another embodiment of the present invention.

FIG. 3B shows a top-down view of a portion of an exemplary IC devicearranged according to another embodiment of the present invention.

FIG. 4 shows a schematic of a portion of an EMI shield region accordingto an embodiment of the present invention.

FIG. 5 shows an exemplary layout of a portion of an IC device accordingto an embodiment of the present invention.

FIG. 6 shows an exemplary layout of a portion of an IC device accordingto an embodiment of the present invention.

FIG. 7 shows an exemplary layout of a portion of an IC device accordingto an embodiment of the present invention.

FIG. 8 shows an exemplary graph comparing electromagnetic coupling as afunction of frequency for a pair of shielded electrical traces inintegrated circuit devices with a conventional EMI shield and EMIshields, according to an embodiment of the present invention.

FIG. 9 shows an exemplary graph comparing input impedance as a functionof time for a shielded electrical trace in integrated circuit deviceswith a conventional EMI shield and EMI shields, according to anembodiment of the present invention.

FIG. 10 shows steps in an exemplary method for designing an IC deviceincluding EMI shields in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

The present invention is described with reference to the attachedfigures, wherein like reference numerals are used throughout the figuresto designate similar or equivalent elements. The figures are not drawnto scale and they are provided merely to illustrate the instantinvention. Several aspects of the invention are described below withreference to example applications for illustration. It should beunderstood that numerous specific details, relationships, and methodsare set forth to provide a full understanding of the invention. Onehaving ordinary skill in the relevant art, however, will readilyrecognize that the invention can be practiced without one or more of thespecific details or with other methods. In other instances, well-knownstructures or operations are not shown in detail to avoid obscuring theinvention. The present invention is not limited by the illustratedordering of acts or events, as some acts may occur in different ordersand/or concurrently with other acts or events. Furthermore, not allillustrated acts or events are required to implement a methodology inaccordance with the present invention.

FIG. 1A shows a cross sectional view of an exemplary POP packageprecursor 100 having a flip chip IC die, according to an embodiment ofthe invention. POP package precursor 100 comprises an electronicsubstrate 106, such as a printed circuit board (PCB), comprising aplurality of electrically conductive layers 125, 126, 127 collectivelyreferred to as conductive layers 108, which are separated by a pluralityof dielectric layers 129, 131, 133. The electronic substrate 106provides a top surface 106(a) and a bottom surface 106(b) and aplurality of electrical conduits 149 for electrically coupling aplurality of locations on the top surface 106(a) to a plurality oflocations on the bottom surface 106(b). A first portion 105 of the topsurface 106(a) has a flip chip oriented IC die 102 having optionalencapsulation material 116 thereon. IC 102 is electrically coupled totop surface 106(a) in first portion 105 by the bumps 157 shown and issecured to the top surface 106(a) by die attach (underfill) material114. A second portion 131 of the top surface 106(a) has a plurality offirst attach pads 141 positioned on opposing sides of the IC die (102)having exposed electrically conductive surfaces for electricallycoupling to at least a first electronic device on top of the IC die 102.As used herein “attach pads” can comprise surface mount (SMT) pads, wirebond pads, flip chip pads, or sockets.

At least a third portion 146 of the top surface area 106(a) ispositioned laterally with respect to the first and second portions105,131 of the top surface 106(a), wherein the third portion 146includes a plurality of second attach pads 147 having exposedelectrically conductive surfaces configured for electrically coupling toat least a second electronic device. The encapsulation material 116 isnot shown over the second 131 and third portion 146 to facilitateadditional assembly activity (i.e. mounting of additional devices). Atleast one of the plurality of electrically conductive layers 125, 126,shown in FIG. 1A as coupling trace 125, electrically couples at leastone of the plurality of second attach pads 147 to at least one of the(i) IC die 102 and (ii) plurality of first attach pads 141.

In one embodiment the IC die 102 comprises digital logic. In anotherembodiment the plurality of first and second attach pads can comprise aplurality of surface mount pads. As shown in FIG. 1A, electricallyconductive layers 126 and 127 provide a shield region for trace 125.“Shield regions” as used herein comprises electrically conductiveregions (e.g. metal lines) that do not provide an interconnect function.Electrically conductive layers 126 and 127 can be seen to be arranged inan overlapping arrangement to provide a coaxial shield region for atleast a portion of a length of trace 125.

Embodiments of the present invention include IC devices (e.g. SIPs) thatinclude digital and analog components that address the EMI noise problemthat can degrade performance of the analog portions and thus theperformance of the overall IC device. Because of the increased proximitybetween the various devices in such an arrangement, EMI interference canbe generated when digital IC devices are placed in proximity to analogICs and discrete devices. As described above, digital devices (and someanalog devices) can generate EMI that can induce significant noise onelectrical traces carrying some types of analog signals. Therefore, insome embodiments of the present invention, EMI shielding and bundling ofreduced dimension lines can be used to further enhance operation of theelectronic device without having to increase trace spacings or reducethe number of signals being exchanged. For example, the PresentInventors have discovered that by placing the EMI generating componentsin only specific portions of the IC device and by shielding electricaltraces that carry EMI sensitive analog signals in these portions of theIC device, the amount of EMI-induced signal degradation can besignificantly reduced.

As described above, embodiments of the present invention provide a ICdevice including a base IC package having at least first and secondportions for attaching and/or stacking analog and/or digital circuitcomponents. In some embodiments of the present invention, the firstportion (EMI-generating portion) can be used for attachingnoise-inducing devices, such as EMI generating digital or analogdevices. The second portion (EMI-passive portion) can be used forattaching other devices EMI passive or EMI resistant devices, such asother types of analog devices or even digital devices generating amountsof EMI insufficient to induce significant noise levels to an electricaltrace that carries a noise susceptible analog signal.

Analog components, as used herein, refers to components or a combinationof components including, but not limited to RF active analog ICs such astransceivers, power amplifiers (PA) and RF crystal (XTL) switchingcircuitry, and passives such as surface acoustic wave (SAW) devices,capacitors, inductors, balons, and resistors. RF active analog ICs, asused herein, refers to analog circuits that during normal operationswitch at frequencies generally >1 MHz. Digital components, as usedherein, refer to components commonly used for processing, transferring,and/or storing data, including, but not limited to: memory modules(SRAM, DRAM, flash memory, etc. . . . ), application specific integratedcircuits (ASICs), base band processors, applications processors, anddigital radio processors.

In other embodiments of the invention, IC die may also be arranged in aface up arrangement. FIG. 1B shows a cross sectional view of anexemplary package-on-package (POP) package precursor 150 having a faceup IC die 152 that includes through wafer vias 154 (also known asthrough substrate vias (TSVs)), according to an embodiment of theinvention. As known in the art, IC die 152 in a face up configurationhaving through wafer vias 154 is adapted for receiving one or aplurality of through wafer via comprising IC die stacked thereon (notshown). Bumps 157 are shown as micro-bumps. IC die 152 generallyincludes a redistribute layer (RDL; not shown) on its backside coupledto through wafer vias 154, wherein the redistribute layer is coupled tothe micro-bumps 157.

FIG. 2A shows an exemplary IC device 200 arranged according to anembodiment of the present invention. IC device 200 can include a basepackage or base IC device 101 comprising a base electronic substrate 106with EMI passive portion 107 and EMI generating portion 103. EMI passiveportion 107 corresponds to third portion 146 shown in FIGS. 1A and 1B.In FIG. 2A, the EMI passive portion 107 is used for attaching one ormore EMI passive components 121 to attach pads on the base substrate 106while the EMI generating portion 103 is used for attaching one or moreEMI generating components shown as first EMI generating IC die 102 andsecond EMI generating IC die 104 stacked on one another and bothattached to attach pads on the base substrate 106.

As used herein, “EMI generating components” refers to analog or digitalcomponents that during operation generate sufficient EMI to induce noisein an electrical trace carrying an analog signal, while “EMI passivecomponents” refers to analog or digital components which generateinsufficient EMI levels to induce noise in an electrical trace carryingan analog signal. The term “electronic substrate”, as used herein,generally refers to any type of PCB used for forming package substrates.In embodiments of the present intervention, electronic substrates can beconstructed using a variety of techniques. By way of example, and not byway of limitation, electronic substrates can be constructed usinglaminate substrate technologies, including rigid and/or flexiblelaminate technologies, and ceramic substrate technologies, includingthin film, thick film, and co-fired (HTCC, LTCC) ceramic technologies.

The base electronic substrate 106 can include a plurality of dielectriclayers 129, 131, 133 and electrically conducting layers 108 to couplecomponents attached to either of portions 103 and 107 to circuitcoupling features 110 of the base electronic substrate 106 or to eachother. For example, as shown in FIG. 2A, first EMI generating IC die 102can be electrically coupled to a first portion 105 of the base substrate106 using one or more electrical bonding features 112 on the first EMIgenerating die 102, the base substrate 106, or both. In the exemplarycircuit in FIG. 2A, a flip-chip arrangement is illustrated. However,embodiments of the invention are not limited in this regard and thefirst EMI generating IC die 102 can also generally be electricallycoupled to the base substrate 106 generally using any other type ofelectrical bonding methods, including wire bonding or tab bondingmethods. The first EMI generating IC die 102 can also be mechanicallycoupled to the substrate 106 generally using any type of adhesivematerial. For example, as shown in FIG. 2A, underfill 114 and/or moldingcompound 116 materials can be used to mechanically couple and protectthe first EMI generating IC die 102 to the base substrate 106.

In some embodiments of the present invention, the first EMI generatingIC die 102 can be a controller or processor IC. Such a configurationallows the base package to be configured with a particular ASIC toprovide basic functionality and permits other EMI passive or EMIgenerating components to be selectively added at a later time. Forexample, in a RF communications package, a customized RF controller IC,which can comprise multiple combinations of EMI sensitive and EMIgenerating components, can be first attached to the base IC device 101and provided to a RF device manufacturer to complete manufacturing ofthe IC device. The RF device manufacturer can customize the IC device101 by attaching the controller IC and the memory device(s) to the EMIgenerating portion 103 and the RF components to the EMI passive portion107 according to device requirements, cost, or other factors.

A second IC device 109, which can include a second EMI generating die104 mounted onto a second electronic substrate 118, can be stacked overthe first EMI generating die 102, for example using a POP arrangement.The POP arrangement can also allow addition IC devices (not shown) to bestacked on top of IC device 109. However, embodiments of the presentinvention are not limited solely to POP-type packages for the second ICdevice 109 and other IC package technologies can be used for forming thesecond IC device 109.

The second electronic substrate 118 can also include a plurality ofdielectric and electrically conducting layers 120 to couple the seconddie 104 to second coupling features 122 of the second electronicsubstrate 118 and/or the base electronic substrate 106. In the exemplarycircuit in FIG. 2A, a flip-chip arrangement is illustrated for the basesubstrate 106 and the second IC device 109. As previously described,embodiments the invention are not limited in this regard and the secondIC device 109 can also be electrically bonded to the base substrate 106using other bonding methods, such as wire bonding, tab bonding or usingthrough wafer via connections if provided. The second EMI generating die104 can be electrically coupled to the second substrate 118 using one ormore electrical bonding features 124 on the second EMI generating die104, the second substrate 118, or both. In the exemplary circuit shownin FIG. 2A, a wire bond arrangement is illustrated for the second EMIgenerating die 104. As previously described, embodiments of theinvention are not limited in this regard and the second EMI generatingdie 104 can also be electrically bonded to the second substrate 118using other bonding methods, such as flip chip, tab bonding or usingthrough wafer via connections. The second EMI generating die 104 canalso be mechanically coupled to the second substrate 118, as describedabove for the first EMI generating die 102 and the substrate 106 usingunderfill (not shown) or molding compound layers 117. In someembodiments of the invention, one or more additional EMI generating dies(not shown) can be stacked on top of the second EMI generating die 104.

In embodiments of the present invention, the EMI generating componentscomprising first and second EMI generating die 102 and 104 are attachedto the base substrate 106 in the EMI generating portion 103, which islaterally positioned with respect to the EMI sensitive portion 107. Thelength of EMI sensitive portion 107 is generally 0.5 mm to 20 mm. Asshown in FIG. 2A, the EMI passive components 121 can be attached to anyportion of the EMI sensitive portion 107. Each of the EMI passivecomponents 121 can be electrically coupled to the base substrate 106(and thus the other components mounted thereon) using one or moreelectrical bonding features 123 on the EMI passive components 121, thebase substrate 106, or both. In the exemplary circuit in FIG. 2A, a wirebond arrangement using bond wires 123 is illustrated for the EMI passivecomponents 121. Embodiments of the invention are not limited in thisregard and the EMI passive components 121 can also be electricallybonded to the substrate 118 using other bonding methods for discretecomponents.

In some embodiments of the invention, the type of bonding and couplingfeatures selected for attaching the EMI passive component 121 and thesecond IC device 109 can be selected to simplify assembly. For example,if reflow-based bonding and coupling features are selected, thenattachment of the EMI passive component 121 and the second IC device 109requires only placement of the components and a single subsequent reflowstep.

As described above, the various components attached to the basesubstrate 106 can be interconnected via the plurality of electricallyconductive layers 108 in the base substrate 106. In embodiments wherethe first EMI generating die 102 is a controller IC for the EMI passivecomponents 121, the EMI passive components 121 and the first EMIgenerating die 102 can be connected via at least one interconnectiontrace 125 in the base substrate 106. However, as previously described,the signals provided on the interconnection trace 125 can be susceptibleto EMI and noise can be introduced into an analog signal carried by thetrace 125, thus being able to adversely affect the operation of the ICdevice 200.

To provide EMI shielding for these EMI sensitive traces 125 in IC device200, a shield region 126 is shown in FIG. 2A which can be formed withinthe base substrate 106 in a area defined by a path of theinterconnection trace 125. In particular, the shield region 126 can beformed between the upper surface of substrate 106 and a portion 137 oftrace 125 extending under the EMI generating portion 103. In someembodiments, a lower shield region 127 can also be provided. In suchembodiments, the coaxial nature of the EMI shielding provided by regions126 and 127 provides enhanced shielding for trace 125. Regardless of thenumber of shield layers, the shield layers can extend over at least amajority of the length of the portion 131 of trace 125. That is, >50%over the length of the portion of the trace 125 under the EMI generatingportion 103.

Although two EMI generating IC die (102, 104) are shown in FIG. 2A, oneof ordinary skill in the art will recognize that the various embodimentsof the present invention can be implemented in IC devices having anynumber of stacked dies, including EMI generating and EMI passive IC die,as well as any number of electronic substrates. Furthermore, althoughembodiments of the present invention provide for placing EMI generatingcomponents within the EMI generating portion, EMI passive components canbe placed in either the EMI generating portion or the EMI passiveportion. Additionally, even though EMI shield layer 126 is shown to be asingle region that extends along the length of the trace 125,embodiments of the invention are not limited in this regard. One ofordinary skill in the art will recognize that the EMI shield layer 126can generally have any size and need only extend over a portion of thearea between the dies. Furthermore, multiple shield regions can be usedto protect different portions of the dies.

For example, FIG. 2B shows a top-down view of a portion of IC device 200shown in FIG. 2A with the substrate 118 and the first EMI generating ICdie 102 removed. In FIG. 2B, three EMI passive components 121 a, 121 b,and 121 c which are coupled to attach pads thereunder (not shown) arecoupled to the bonding features in first die area 105 via the attachpads which are coupled to first die area 105 via traces 125. In portion107, discrete devices 141, such as resistors and capacitors are shownattached to some of the plurality of attach pads 142 provided. Toprotect the signals on traces 125 from noise pick up, shields 126 a, 126b, and 126 c are provided for shielding each set of traces 125 couplingto different ones of EMI passive components 121 a, 121 b, and 121 c.However, embodiments of the invention are not limited in this regard andshield regions 126 a, 126 b, and 126 c can be merged in some embodimentsto form a single shield area 126 d (shown by the dashed line).

Although FIGS. 2A and 2B only show an IC device having a substrate withEMI generating dies and adjacent EMI passive components attacheddirectly to the same base substrate 106, embodiments of the inventionare not limited in this regard. In some embodiments, the EMI passivecomponents can be attached to EMI passive dies that can be disposed inthe EMI passive portion 107. Such a configuration is shown in FIGS. 3Aand 3B.

In FIG. 3A, a cross-section of an IC device 250 configured according toan embodiment of the present invention is shown. IC device 250 issimilarly configured to IC device 200 shown in FIG. 2A with respect tothe stacking of EMI generating dies in the EMI generating portion 103.However, as shown in FIG. 3A, the base package 151 includes a basesubstrate 106 in EMI passive portion 154 configured for forming astacked or POP arrangement of EMI passive components 121.

As shown in FIG. 3A, the EMI passive components 121 can be mounted ontoa third electronic substrate 168 stacked over the EMI passive interfaceregion 154. The third electronic substrate 168 can also include aplurality of dielectric and electrically conducting layers 160 to coupleat the EMI passive components 121 to third coupling features 162 of thethird electronic substrate 168 and/or the base electronic substrate 156.In the exemplary circuit in FIG. 3A, a flip-chip stacked arrangement isillustrated for the base substrate 156 and the third substrate 168. Aspreviously described, embodiments of the invention are not limited inthis regard and the third substrate 168 can also be electrically bondedto the base substrate 156 using other bonding methods, such as wire bondor tab bonding. The EMI passive components 121 can be electricallycoupled to the third substrate 168 using one or more electrical bondingfeatures 164 on the EMI passive components 121, the third substrate 168,or both. In the exemplary circuit in FIG. 3A, a wire bond arrangement isillustrated for the EMI passive components 121. As previously described,embodiments of the invention are not limited in this regard and the EMIpassive components 121 can also be electrically bonded to the thirdsubstrate 168 using other bonding methods, such as flip chip or tabbonding.

The EMI passive components 121 can also be mechanically coupled to thethird substrate 168, as described above for the first EMI generating die102 and the base substrate 106 as shown in FIG. 3A using underfill (notshown) or molding compound layers 167. Although discrete EMI passivecomponents 121 are illustrated in FIG. 3A, embodiments of the inventionare not limited in this regard. In some embodiments, the EMI passivecomponents can comprise EMI passive IC dies or a combination of EMIpassive IC dies and discrete EMI passive components. In embodimentsusing EMI passive IC dies, one or more additional EMI passive IC dies(not shown) can be stacked on top of other EMI passive IC dies, aspreviously described for EMI generating dies in FIG. 3A.

Although the EMI passive portion 154 is configured for forming a stackedarrangement of EMI passive components, the shield region 126 can besimilarly configured as described above with respect FIGS. 2A and 2B.For example, FIG. 3B shows a top-down view of IC device 250 shown inFIG. 3A with the third substrate 168, the second substrate 118, and thefirst EMI generating die 102 removed. As described above, one or moreshield regions 126 can be formed over the traces that carry noisesusceptible analog signals.

The Present Inventors note that the basic requirements for forming aneffective EMI shield to protect EMI sensitive portions is that theshield should be formed of an electrically conductive material (e.g.metal or highly doped semiconductor) and have a sufficient thickness.That is, the thickness should be sufficiently large such that the EMIaffects only an outer portion of the thickness (the frequency dependentskin depth) of the EMI shield layer. The thickness required can vary asthe electrical conductivity of the enclosure material varies and as thetype of EMI varies. Generally, as electrical conductivity of the shieldlayer material increases, the thickness of material required to blockEMI decreases and vice versa. Therefore, an electromagnetic shield layerrequires a layer that is not only electrically conductive, but that hasa thickness greater than a skin depth for the EMI to be blocked. Incases where the EMI generating IC is shielding the EMI source, the sameprinciples generally apply with the exception that skin depth ismeasured from the interior of the enclosure. For example, in oneparticular embodiment, the electrical conductive (e.g. metal) shieldlayer thickness for providing adequate shielding from adjacentRF-generating IC's and/or trace can be at least 10 um of an alloyprimarily comprising copper, such as between 15 and 20 um thick.

In embodiments of the present invention, various shield layer designscan be used to block EMI. In some embodiments, solid shield regions canbe formed. However, a solid configuration can result in poor adhesionbetween the multiple layers of the base substrate and can lead toreliability failures of the base substrate due to delamination. In otherembodiments, a shield layer having a regular pattern of non-planarfeatures such as openings can instead be used. However, if the area ofthe openings is too large, some wavelengths of generated EMI canpenetrate the shield. Therefore, to provide adequate adhesion andsufficient EMI blockage, some embodiments of the present inventionprovide an EMI shield region having solid areas overlapping EMI reactivetraces and having an aperiodic arrangement of openings elsewhere. A“solid area” of the EMI shield region, as used herein, refers to an areaof the EMI shield region having no openings in the EMI shield layer.

FIG. 4 shows a schematic of a portion of an IC device 400 including anEMI shield region according to an embodiment of the present invention.As shown in FIG. 4, IC device 400 can include one or more electricaltraces 302 that need to be shielded from EMI generated by a firstfunctional die 303 (footprint shown by dashed lines), an electronicsubstrate 301, or a second functional die 305 (footprint shown by dashedlines). Although a first functional die 303 is shown to be smaller thanboth the second functional die 305 and the electronic substrate 301,embodiments of the invention are not limited in this regard. Inembodiments of the present invention, the sizes of the variouscomponents can vary according to the design required for the IC device300.

In embodiments of the present invention using aperiodic openingarrangements in the shield layer, at least one shield region 304 can beformed for the IC device 400 on the electronic substrate 301. The shieldregion 304 can be coupled to a grounding terminal 310 of the IC device400. To provide sufficient EMI shielding, the shield region 304 caninclude at least one solid area 306 and one or more enhanced adhesionareas 307 having one or more openings 308. In some embodiments, theshield region 304 can have a width equal to that of the shielded trace302 to be shielded (i.e., W_(O)=0). In other embodiments, the shieldregion 304 can overlap the edges of the traces 302 by at least a minimumamount W_(O). Such an overlap reduces EMI reaching the traces 302 fromEMI generating portions of dies 303 or 305 via diffraction effects atthe edges of the shield region 304 or due to EMI traversing the ICdevice at angles other than perpendicular to the shield region 304.Accordingly, one of ordinary skill in the art will recognize that theminimum trace overlap W_(O) can vary as the distance between the traces302 to be protected and the shield region 304 varies.

As described above, the openings 308 in the shield region 304 areprovided for promoting adhesion of the shield region 304 to theelectronic substrate 301 underneath the shield region 304. Accordingly,as shown in FIG. 4, the adhesion regions 307 can include one or moreopenings 308 that provide a sufficient surface area to promote goodadhesion. In the various embodiments of the present invention usingaperiodic opening arrangements in the shield layer, the width of theopenings 308 can vary between 10 um and 300 um, such as 50 um, 100 um,150 um, and 300 um. Furthermore, to further ensure a sufficient area topromote reliable adhesion of the shield region 304, the number and sizeof the openings 308 can be selected depending on process conditions, ICdesign, and package design. Typically, as the area of the openings isincreased, less shielding is provided, albeit with better adhesion. Asthe area of the openings is decreased, more shielding is provided, butwith less adhesion. As one of ordinary skill in the art will recognize,the number and size of openings may be ultimately limited based on thewavelength of the EMI in question and the particular manufacturingprocess. For example, some electronic substrate materials can require alarger surface area for reliable adhesion. Therefore, the area of theopenings can comprise between 30% and 80% of the total area of theshield region 304. In some embodiments, this range can be limited basedon process conditions to between 35% and 75% or between 30% and 70%.

Although FIG. 4 only shows round openings 308 having the same size, thevarious embodiments of the present invention are not limited in eitherof these regards. For example, in embodiments of the present inventionusing aperiodic opening arrangements in the shield layer, openings ofany geometry, including that of polygons, ellipses, or other shapes, canbe used to form openings.

In embodiments of the present invention using aperiodic openingarrangements in the shield layer, the number and position of theopenings can also vary depending on the total area and geometry ofportions 312 of the shield region 304 extending beyond the edges of thetraces 302. Although the extending portion 312 is shown in FIG. 4 toextend from an edge of the electrical trace 302 to the edge of theshield region 304, embodiments of the present invention are not limitedin this regard. In some embodiments of the present invention usingaperiodic opening arrangements in the shield layer, extending portions312 (and thus the enhanced adhesion areas 307) can be bounded by one ormore electrical traces, by one or more edges of the shield region 304,or any combination thereof.

As the number of openings 308 in an shield region 304 is increased, anincreased area of the electronic substrate 301 is exposed and thelikelihood of good adhesion of the underfill and molding layersgenerally increases. However, as the size of the openings is furtherincreased or their spacing is decreased, the openings 308 can becomemore poorly formed in the shield region 304. In some cases, this cancause some of the openings 308 to encroach on the solid portions 306.This encroachment can reduce the effectiveness of the shield region 304in blocking EMI. Therefore, in the various embodiments of the presentinvention using aperiodic opening arrangements in the shield layer, theposition and number of openings can be dependent on one or more designrules. The design rules can be used to then determine the maximum numberof openings can be placed without significantly affecting the integrityof the solid areas 306 of the EMI shield region. That is, the designrules ensure that after the integrated circuit device 400 is formed, thesolid areas 306 remain of a sufficient width to block EMI, as previouslydescribed.

A first design rule can be that the distance (x) between the edge of anopening 308 and an edge of the shield region 304 should be greater thanor equal to a minimum edge to edge spacing. A second design rule can bethat the distance between adjacent openings 308 should also be greaterthan or equal to a minimum edge to edge spacing (y). One of ordinaryskill in the will recognize that this spacing can be the same ordifferent in the various embodiments of the present invention. The thirddesign rule can be that the minimum lateral distance between any tracesbeing shielded and an edge of an opening 308 should be at least theminimum width (W_(O)) for the shield region. Accordingly, one ofordinary skill in the art will recognize that for a round opening 308having a diameter d, the extending portion 312 needs to have at least anarea equal to W_(E)·L, where L≧d+2x and W_(E)≧x+d+W_(O). However, theinvention is not limited in this regard. In some embodiments, an opening308 can overlap with an edge of the shield region 304 (i.e., x≦0) asshown by edge 316 in FIG. 4.

The aperiodic arrangement of openings results because the arrangement ofthe openings is based on the geometry of each of the individual enhancedadhesion areas as opposed to the overall geometry of the EMI shieldregion. Accordingly, variations in the area and geometry of eachenhanced adhesion area results in variations in the number and placementof openings. However, the shield layers are not limited to solely anaperiodic distribution of openings of a single size, as shown in FIG. 4,but can include an aperiodic distribution of openings of differentsizes, as shown in FIG. 5. The different sizes allow smaller openings tobe inserted in adhesion regions that would not typically allow placementof larger sized openings.

Such a configuration can be advantageous for reducing the amount ofsolid portions of the shield region. For example, referring back to FIG.3B, the traces 125 are shown connecting coupling features 112 alonglength a to coupling features 162 along length c and separated bydistance d. If a straight line path were to be used to couple thefeatures 162 and 112, the area of the shield region would be defined bythe perimeter based on dimensions a, c, and d. However, as shown in FIG.3B, if at least portions or segments 164 or of the traces are place inclose proximity or “bundled” along a common path area 166, at least aportion of the shield 126 can be narrowed to a width b improve adhesionby reducing the overall area of the shield 126. That is, at leastsegments 164 of the traces 125 between the EMI sensitive portion 107 andEMI generating portion 103 are placed to provide a minimum spacing. Suchpositioning or repositioning of bundled segments 164 can occur duringinitial design of the base substrate 106 or during placement of theshield region 126. Although only a single bundle is shown in FIG. 3B,one of ordinary skill in the art will recognize that any number ofbundles and/or path areas can be used in other embodiments. For example,as shown in FIG. 2B, three path areas 140 a-c are shown. However, inareas of the shield 126 where the traces 125 begin to separate 126(areas e and f), the spacing between the traces 125 may be insufficientfor placing openings to improve adhesion. In such cases, placement ofsmaller sized openings in areas e and f between traces 125 provesenhanced adhesion within the base substrate 156 while maintainingsufficient shielding of EMI generated by traces 125. This concept isillustratively shown in FIG. 5.

FIG. 4 shows an exemplary layout of a portion of an IC device 500according to an embodiment of the present invention. In particular, FIG.5 shows an IC device layout 500 with a shield region 402 formed in anelectronic substrate. The EMI shield region includes at least a firstenhanced adhesion area 406 having openings 420. In FIG. 5, the firstadhesion area 406 is bounded by EMI reactive electrical traces 410, 412,and 414. In enhanced adhesion area 406, the spacing between theseadjacent traces 410, 412, and 414 is insufficient to allow placement ofa large size opening, such as opening 416. However, the spacing issufficient to allow placement of one or more openings of a smaller size420. Accordingly, in these smaller enhanced adhesion areas, smallersized openings 420 can be used. In some embodiments, in addition toutilizing smaller sized openings 420, the design rule spacing utilizedcan also be decreased, as the processing margin for forming such smalleropenings 420 is typically larger.

As described above, the openings in the EMI shield region can vary insize. Accordingly, one of ordinary skill in the art will recognize thatthe electrical traces 410, 412, and 414 need not have openings of thesame size on both sides. Rather the selection of opening size in aparticular portion of the shield region 402 is determined based on itsarea and geometry. For example, as shown in FIG. 5, other openings 421surrounding the traces 410 and 412 include openings of a larger size420.

In addition to using openings of different sizes in different enhancedadhesion areas, in some embodiments, a mix of differently sized openingscan be used in a single enhanced adhesion area. FIG. 6 shows anexemplary layout of a portion of an IC device 600 according to anembodiment of the present invention. In IC layout 500, openings of botha larger size 502 and a smaller size 504 are used in enhanced adhesionarea 506. In enhanced adhesion area 506, the portion bounded only bytraces 508 and 510 allow placement of openings of a larger size 502.However, in areas of portion 508 also bounded by traces 510 and 512, theremaining spacing is insufficient for such larger openings 502. In suchareas, openings of a smaller size 504 are used instead. In some cases,no openings can be inserted. For example, in the portion of enhancedadhesion area 506 bounded by traces 512 and 508, insufficient spacing isprovided for insertion of an opening of any available size. In suchcases, the portion would remain solid.

In some embodiments of the present invention, additional openings canalso be included in the EMI shield region to improve adhesion along anedge of the EMI shield region or along portions of the EMI shield regionin proximity with an edge of the functional die being mechanicallyattached. This can result in improved resistance against delaminationalong such edges. FIG. 7 shows an exemplary layout of a portion of an ICdevice 700 according to an embodiment of the present invention. Inparticular, FIG. 7 shows an IC device 700 where a portion 602 of an EMIshield 604 that is to be in proximity with an edge of a functional dieto be attached is shown. In this portion 602, large size openings 606can be provided for electrical coupling of the electronic substrate to adie. Typically, the size of such openings is sufficiently large toexpose a sufficiently large surface area of the electronic substrate andensure proper adhesion. However, because stress is typically enhanced insuch regions, in embodiments of the present invention, additionalopenings of a smaller size 608 can be placed along the edges of the EMIshield region 604 to increase the area and thus the amount of theadhesion.

As described above, EMI shield layouts with aperiodic openingarrangements can generally be used to block EMI while promoting adhesionwithin the base electronic substrate. FIG. 8 shows the admittance ratio(y₁) for a pair of EMI sensitive traces in the stacked integratedcircuit device as a function of frequency, wherein the IC deviceincludes a digital radio IC and a digital memory and processor ICconfigured in a stacked arrangement. For EMI sensitive circuits, theresult of EMI interference is typically an increase in coupling betweencircuit elements, resulting in a decrease of the admittance ratio y₁ dueto the increase of EMI-induced impedance. As shown in FIG. 8, over thefrequency range of 0 to 5 GHz, the admittance ratio values 702 for an ICdevice having a conventional periodic cross-hatched EMI shield region isshown to be approximately 4-6 dB lower (demonstrating increasedcoupling) as compared admittance ratio values 704 for an IC devicehaving an EMI shield region according to the various embodiments of thepresent invention.

As described above, EMI directly impacts the impedance of EMI sensitivetraces. In particular, the characteristic impedance or surge impedancecan also be affected by EMI, and can result in poor impedance controlduring operation of an IC in an IC comprising device. FIG. 9 shows anexemplary graph comparing input impedance as a function of time for ashielded electrical trace in IC devices with a conventional EMI shieldand EMI shields according to an embodiment of the present invention. Inparticular, FIG. 9 shows the characteristic impedance of an EMIsensitive electrical trace in an integrated circuit device including adigital radio integrated circuit and a digital memory and processorintegrated circuit configured in a stacked arrangement. FIG. 9 showsimpedance of the electrical trace as function of time. As shown in FIG.9, over time period between 0 and t₁ (≦1 ns) the impedance of theelectrical trace varies regardless of the EMI shield region design beingused. Over the time period between t₁ and t₂ and beyond (≧1 ns), theimpedance reaches a steady state value that is approximately equalregardless of the EMI shield region deign being used. However, as shownin FIG. 9, the magnitude of variation in impedance values 802 for an ICdevice having a conventional periodic cross-hatched EMI shield region isshown to be greater as compared the magnitude of variation in impedancevalues 804 for an IC device having an EMI shield region according to anembodiment of the present invention. Accordingly, including an EMIshield region according to the various embodiments of the presentinvention improves impedance control. Such control can be criticalespecially when the frequency at which signals are being applied to theEMI sensitive traces is high, since the resulting characteristicimpedance will generally be a function of the amount of such switching.

In embodiments of the present invention using aperiodic openings, adesign for the EMI shield region can be generated in various ways. FIG.10 shows steps in an exemplary method 900 for designing an IC deviceincluding EMI shields in accordance with an embodiment of the presentinvention. Method 900 can be implemented manually by a circuit designeror can be implemented automatically in a design tool including automaticlayout and error checking capabilities.

First, in step 902 the design of the electronic substrate(s) can beobtained, as well as the designs for any functional die normallyincluded with the electronic substrate design. For example, aspreviously described, the base electronic substrate can be provided toan RF device manufacturer including a controller IC. Therefore, in step902, the locations of the EMI passive portions and EMI generatingportions can be provided, along with the locations of electrical tracesconnecting the two interfaces. Once the design is obtained in step 902,one or more traces in the base substrate that will carry EMI susceptible(e.g. analog) signals can be identified in step 904. This identificationcan be based on the types of circuits the base substrate is designed tooperate with or based on empirical data available for the particular ICdevices. After these traces are identified in step 904, the location forthe EMI shield region can be determined in step 906. That is, anappropriate location within the electronic substrate for the EMI shieldregion can be selected based on the location of the traces identified instep 904. In some embodiments, the position of the EMI generating tracesin the base substrate can be adjusted in step 905 prior to determining afinal location for the EMI shield region in step 906. For example, theEMI generating traces can be bundled along a common path area 126 asdescribed above with respect to FIG. 3B. This can allow the size of theshield region to be reduced, improving adhesion in the base substrate.

Once the location for the shield region(s) is selected in step 906, theEMI shield region can be defined. Initially, in step 908, the solidareas for the EMI shield region can be determined based on the locationsof the traces identified in step 904. The placement of solid areas canbe also adjusted as needed to accommodate the presence of other circuitsin the base electronic substrate. For example, the design can beadjusted to prevent shorting of circuit elements to the EMI shieldregion.

Step 910 comprises identifying extending portions in the EMI shieldregion for use as enhanced adhesion areas. In step 912, the location andsize of openings in the identified enhanced adhesion areas can bedetermined. The location and size of the openings can be determined inseveral ways. For example, in some embodiments a first enhanced adhesionarea and a first size of opening can be selected. Based on the designrules, a maximum number of openings of the first size can be placed inselected enhanced adhesion area. In other embodiments, a second size canthen be selected and a maximum number of openings of the second size canbe placed in the remaining portions of the selected enhanced adhesionarea. This can be repeated for other sizes of openings. The method canthen be repeated for other enhanced adhesion areas. In still otherembodiments, as previously described, once other openings are placed,the regions in proximity to the edge of the EMI shield region or theedge of the functional circuit die to be attached to the electronicsubstrate can be selected and additional openings can be inserted toenhance adhesion.

These are but a few examples. Accordingly, the breadth and scope of thepresent invention should not be limited by any of the above describedembodiments. Rather, the scope of the invention should be defined inaccordance with the following claims and their equivalents.

Although the invention has been illustrated and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art upon the reading andunderstanding of this specification and the annexed drawings. Forexample, in embodiments of the invention including a transceiver, anantenna coupled to the transceiver may be formed on the same electronicsubstrate. In particular regard to the various functions performed bythe above described components (assemblies, devices, circuits, systems,etc.), the terms (including a reference to a “means”) used to describesuch components are intended to correspond, unless otherwise indicated,to any component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure which performs thefunction in the herein illustrated exemplary implementations of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one of several implementations,such feature may be combined with one or more other features of theother implementations as may be desired and advantageous for any givenor particular application. Furthermore, to the extent that the terms“including”, “includes”, “having”, “has”, “with”, or variants thereofare used in either the detailed description and/or the claims, suchterms are intended to be inclusive in a manner similar to the term“comprising.”

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the following claims.

1. A method of forming a package-on-package (POP) comprising integratedcircuit (IC), comprising: providing POP package precursor, comprising anelectronic substrate comprising a plurality of electrically conductivelayers separated by a plurality of dielectric layers, said electronicsubstrate providing a top surface; a first portion of said top surfacehaving an IC die attached thereto having; a second portion of said topsurface having a plurality of first attach pads positioned on opposingsides of said IC die having exposed electrically conductive surfaces forelectrically coupling to at least a first electronic device on top ofsaid IC die, and at least a third portion of said top surface positionedlaterally with respect to said first and said second portion of said topsurface, said third portion including a plurality of second attach padshaving exposed electrically conductive surfaces for electricallycoupling to at least a second electronic device, wherein at least one ofsaid plurality of electrically conductive layers comprises a couplingtrace that electrically couples at least one of said plurality of secondattach pads to at least one of said IC die and at least one of saidplurality of first attach pads. coupling at least a first electronicdevice to said plurality of first attach pads and positioned on top ofsaid IC die, and coupling at least a second electronic deviceelectrically to said plurality of second attach pads.
 2. The method ofclaim 1, wherein said IC die provided in said providing is anencapsulated IC die having encapsulation material thereon, said firstelectronic device comprises a memory module, and said second electronicdevice comprises an RF circuit.